Process for the preparation of higher alkyl esters of the carboxylic acids



. boxylic acids and Patented Apr. 30, 1935 THE PREPARATION 0F.

Es'rEiss PRGQESS roe arenas Atari. Boxymo ACIDS Donald J. Loder,

E. R. du Pont OF THE CAR-' Wilmington, Del assignor to de'Nemours &Company,

Wil-

mington, Del.,a corporation of Delaware I N0 Drawing."

Serial This'invention relates to'a process for the prep 'aration of thehigher alkyl esters of the carmore particularly to the preparation ofthe higher alkyl esters of the aliphatic carboxylic acids from the loweralkyl esters thereof.

Esters are ordinarily prepared by direct esterificatiomthat is by directaction oi the acid on the alcohol. It is well known cation by the directesterification process is extremely slow and particularly so when'thehigher acids are reacted with the higher alcohols. Furthermore, thehigher alcohols to preparation of the higher alkyl esters are generallyexpensive which results in a product too costly for general use.

An object of the present invention is to provide a simple and economicalprocess for the preparationof higher alkyl esters. Another object of thepresent'invention is to provide a. process for the preparation of thehigher alkyl esters of the carboxylic' acids from .thelower alkyl estersof those acids. A further object of the invention is to provide aprocess for the preparation of the higher alkyl esters ofthe carboxylicacids by the steps of halogenating a lower alkyl ester of the acid,condensing the halogenated ester with an olefinic hydrocarbon, andfinally dehalogenating the resulting higher alkyl ester. A still furtherobject of the invention is to provide optimum conditions and highlyefiicient cat alysts for use in carrying out such processesi Otherobjects and advantages of the invention will hereinafter appear. I

I have found that the higher alkyl esters can 1 be preparedreadily andeconomically by halogenating the lower alkyl ester, condensing it withan olefinic hydrocarbon, and finally dehalogenating the resulting higheralkyl ester. A still further object of the invention is to provideoptimum conditions and highly efficient catalysts for use in carryingout such 'processes, Other objects and advantages of the invention willhereinafter appear.

I have found that the higher alkyl esters can be prepared readily andeconomically by halogenating the lower alkylester, condensing it with anolefinic hydrocarbon, and finally dehalogenating the resulting'higher.alkyl ester. The esterforming reaction apparently proceeds in accordwith the following equations in which halogens other than chlorine may,of course, be used:

nooonlxo1+nz=acooaixn+ncr (s) that esterifibe used in the.

higher aliphatic .acidssuch,

alkyl ester. and react it Application wit-a925, 193s,"

t e Claims. (01. 260-106) The compounddesignated as RCOORrl-lin thehalogenation reaction designated as Reaction (1) may have substitutedfor R any alkyl, aryl, or aralkylgroupi.ng' and R1 any alkylene,arylene, or aralkylene grouping, while the X of Equation (2)v designatesany olefinic hydrocarbon. Thus, by the substitution of a methyl groupfor ,R and R1, and the olefine, ethylene, for X, propyl acetate isproduced from methyl acetate; i

' CHsCOOCl-ls+Cl2=CH3COOCH2Cl+HC1 CHSCOOCH2C1+CH2ZCH2=CH3COOC3H6C1 ICl-IsCOOCsHsCl+H2=CH3COOC3Hv+HC1 Propylene and butylene similarly yieldthe butyl ester and amyl ester of aceticacid respectively.

Esters suitable for use in my process are read ily available from anumber of sources. They may be prepared from the primary, secondary, ortertiaryalcohols by simple esterification, by ester interchange, or byany suitable process and include,I for example, the alkyl esters of thealiphatic carboxylic acids generallly, i. e. such esters asrnethyl,ethyl, propyl, butyl, and higher alkyl esters jof'acetic, propionic,butyric, and even the for example, as oleic,

palmitic, stearic,,and the like. It is tobeunderstood that my process isprimarily directed to the preparation of the higher alkyl'esters, fromthe lower alkyl estersyand in lieu of condensing a high allaylesterofacetic acid, 1 such as ethyl acetate, withethylene, in order toobtain a butyl ester, for example, I usually prefer to use a lower witha higher olefine, for example the'methyl ester with utylene to get the'amyl ester. .Nor do I limit'myseli to the condensation of the olefinewith the saturated esters, of the..monocarboxylicacid for theunsaturated esters and polycarboxylic acid 4 esters, for example methylacrylataethyl acrylate, -methyl citrate, ethyl tartratefand' equivalentestersmay likewise be used, in acccrd'with my invention,for thepreparation of their corresponding higher esters. It is not essentialthat a condensed with an higherester, for a mixture or esters maybe usedsuch as are obtained by esterification of the oxygenated organiccompounds, principally alcohols, which areobtained by the catalytichydrogena tion of carbon oxides under pressure according t o the processdescribed by E; F; lzard. in U. S; appli-' cation Ser. No. 6565166.'Theproduct obtained; by condensation of these esters inv accordwith, myprocess will-give higher alkyl esters offthis mixture of {oxygenated Yorganic-compounds;

Furthermore, aromatic esters, such, 'for example,

singleester be olefine to obtain a single it is desired to convert beemployed in a 'rela tively high degree of purity.

The halogenation of the lower alkyl ester may,

be carried out by any suitable halogenation process, for example bypassing chlorine into the liquid ester at a suitable temperature andpressure, such, for example, as from 0 to the boiling of approximatelyC. and a pressure of approximately 50 atmospheres have been foundsuitable for many condensations of this type.

c Any suitable dehalogenation process may be Ewample.Methyl acetate(into which 0.5%

pressure at a temperature'of C. product is fractionated to removechloromethyl acetate.

unchanged 7 e chlorobutyl acetate may be distilled to purify it. In caseit is desired 7 carbon,- thus condensed halogenated 5. A process forogenated' and condensed ester.

6. A process for the ester with an olefinic hydrocarbon.

8. In a process for the preparation of the higher alkyl esters of theorganic carboxylic acids from the lower halogenated alkyl an: olefinichydrocarbon.

DONALD}. LODER.

preparation of propyl

